ceph/src/boost/libs/coroutine2/include/boost/coroutine2/detail/create_control_block.ipp

   1
   2 //          Copyright Oliver Kowalke 2014.
   3 // Distributed under the Boost Software License, Version 1.0.
   4 //    (See accompanying file LICENSE_1_0.txt or copy at
   5 //          http://www.boost.org/LICENSE_1_0.txt)
   6
   7 #ifndef BOOST_COROUTINES2_DETAIL_CREATE_CONTROLBLOCK_IPP
   8 #define BOOST_COROUTINES2_DETAIL_CREATE_CONTROLBLOCK_IPP
   9
  10 #include <cstddef>
  11 #include <memory>
  12 #include <utility>
  13
  14 #include <boost/assert.hpp>
  15 #include <boost/config.hpp>
  16
  17 #include <boost/context/preallocated.hpp>
  18 #include <boost/context/stack_context.hpp>
  19
  20 #include <boost/coroutine2/detail/config.hpp>
  21
  22 #ifdef BOOST_HAS_ABI_HEADERS
  23 #  include BOOST_ABI_PREFIX
  24 #endif
  25
  26 namespace boost {
  27 namespace coroutines2 {
  28 namespace detail {
  29
  30 template< typename ControlBlock, typename StackAllocator, typename Fn >
  31 ControlBlock * create_control_block( StackAllocator salloc, Fn && fn) {
  32     auto sctx = salloc.allocate();
  33     // reserve space for control structure
  34 #if defined(BOOST_NO_CXX11_CONSTEXPR) || defined(BOOST_NO_CXX11_STD_ALIGN)
  35     void * sp = static_cast< char * >( sctx.sp) - sizeof( ControlBlock);
  36     const std::size_t size = sctx.size - sizeof( ControlBlock);
  37 #else
  38     constexpr std::size_t func_alignment = 64; // alignof( ControlBlock);
  39     constexpr std::size_t func_size = sizeof( ControlBlock);
  40     // reserve space on stack
  41     void * sp = static_cast< char * >( sctx.sp) - func_size - func_alignment;
  42     // align sp pointer
  43     std::size_t space = func_size + func_alignment;
  44     sp = std::align( func_alignment, func_size, sp, space);
  45     BOOST_ASSERT( nullptr != sp);
  46     // calculate remaining size
  47     const std::size_t size = sctx.size - ( static_cast< char * >( sctx.sp) - static_cast< char * >( sp) );
  48 #endif
  49     // placment new for control structure on coroutine stack
  50     return new ( sp) ControlBlock{ context::preallocated( sp, size, sctx),
  51                                    salloc, std::forward< Fn >( fn) };
  52 }
  53
  54 }}}
  55
  56 #ifdef BOOST_HAS_ABI_HEADERS
  57 #  include BOOST_ABI_SUFFIX
  58 #endif
  59
  60 #endif // BOOST_COROUTINES2_DETAIL_CREATE_CONTROLBLOCK_IPP